This invention relates to electric motors or to other dynamoelectric machines, and more particularly, to an improved centrifugal actuator for actuating a motor starting switch which in turns controls energization of the starting winding in the motor in response to the speed of rotation of the motor.
In many conventional electric motors, such as single-phase induction motors, a rotating magnetic field is produced by means of a main winding and a starting winding included within the stator assembly of the motor. These windings are so designed and arranged within the motor that during start up of the motor, sufficient starting torque is obtained. Once the motor reaches a predetermined operational speed, a switch responsive to the rotational speed of the motor is opened to deenergize the starting winding. Upon the motor speed slowing below another predetermined speed of operation (e.g., due to load conditions or upon shut down of the motor) the switch is closed so that it will energize the starting winding of the motor.
As shown in U.S. Pat. Nos. 3,271,602 and 3,609,421, prior art centrifugal actuators are rotatable With a rotor shaft and include a centrifugal weight assembly, the latter including a pair of centrifugal weighted levers pivotally mounted on a sleeve. The sleeve, in turn, is mountable on the rotor shaft and is intended to be movable thereon. Upon the shaft rotating at a predetermined speed, the weights are thrown outwardly by centrifugal force thus causing the levers to pivot which in turn effects axial shifting movement of the sleeve of the centrifugal actuator with respect to the rotor shaft. This axial movement of the sleeve of the centrifugal actuator assembly in one direction from a so-called first or starting position to a second or run position upon acceleration of the motor to its predetermined operational speed effects the opening of a starting switch associated with the motor by relieving pressure on an actuator arm of the switch.
Typically, the sleeve of the centrifugal actuator, which is operated by the centrifugal levers, is moved along the shaft in a linear motion. The sleeve has a flat collar portion that engages the start switch to close the switch when the rotational speed of the rotor is not sufficient to overcome a biasing of force exerted on the levers. The centrifugal levers are resiliently biased toward their starting position by means of bias springs.
Centrifugal actuators known to the prior art are also disclosed in U.S. Pat. Nos. 4,242,607, and 4,205,245 to Hildebrandt et al. and U.S. Pat. No. 4,661,732 to Gerht. With many of the centrifugal actuators known to the prior art, typically the levers are formed of metal and have centrifugal weight attached to a portion thereof. The levers are pivotally connected to the actuator sleeve. Generally the lever is formed with leg portions extending outward from the weight bearing portion. The leg portions of the levers straddle an outwardly extending shoulder segment of the main body of the sleeve with the tips of the leg portions pivotally seated in notches or slots or other seating means formed in the shoulder portion of the sleeve member. During the assembly of these centrifugal actuators, the centrifugal levers are placed, legs up, on an assembly fixture. The sleeve is assembled onto a base and placed over the upwardly positioned lever legs. The bias springs are applied and the ends of the levers are manually inserted in the lever seats on each side of the sleeve. Prior art designs of the sleeve require that the seating of the levers be done manually to ensure that the leg portions of the levers are properly seated in the lever seats. This is a time consuming and labor intensive process which does not lend itself to an automated assembly procedure. Furthermore, motors having actuators assembled this fashion do not always operate properly in the field because they sometimes have misassembled actuators.
It is, therefore, an object of the present invention to provide a centrifugal actuator having a sleeve with lead ramps extending upward to the lever seats so that the end portions of the lever legs slide up the ramps into the lever seats during assembly, thereby assuring proper seating of the levers in the sleeve portion.
Another object of the invention is to provide a centrifugal actuator assembly having a sleeve with mounting ramps leading to the lever leg seats so that the lever legs can slide into the seats without misaligning during assembly process thereby permitting automated assembly of the actuator.
Another object of the present invention is to provide a centrifugal actuator assembly in which the lever legs can be properly seated in the sleeve notches before field assembly thereby preventing failure and field returns.